Flexible organic electronic device with improved resistance to oxygen and moisture degradation

ABSTRACT

Flexible composite barrier structures are used to improve the resistance, to oxygen and moisture degradation, of an organic electronic device including at least one active layer comprising an organic material.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to organic electronic devices in which theactive layer is an organic material. More particularly, it relates toelectronic devices covered by flexible composite barrier structures.

[0003] 2. Description of the Related Art

[0004] Organic electronic devices include devices that emit light (suchas light-emitting diodes that make up displays) or respond to radiantenergy (such as photodetectors). Displays may contain active matrixaddressing or passive matrix-addressing. In passive matrix displaysthere is an array of electrode lines for addressing individual pixelsarranged in rows and columns; applying a voltage between a particularrow and column energizes the pixel with that corresponding address. Byanalogy with active matrix liquid crystal displays, the polymerelectronic device (display) can be addressed at individual pixels usinga thin film transistor (TFT) device which switches that pixel on andoff. In such a configuration each TFT is electrically connected by to“gate busline” and to “data busline” that also need to be connected tothe electrical driver circuitry and thus sealed outside the activedevice area.

[0005] In all such devices, an organic active layer is sandwichedbetween two electrical contact layers. At least one of the electricalcontact layers is light-transmitting so that light can pass through theelectrical contact layer. The organic active layer may generate anelectric signal in response to light through the at least onelight-transmitting electrical contact layer, or may emit light throughthe light-transmitting electrical contact layer upon application ofelectricity across the electrical contact layers. In the latter case,the organic active layer contains an electroluminescent material.

[0006] It is well known to use organic electroluminescent materials asthe active materials in light emitting diodes. Simple organic moleculessuch as anthracene, thiadiazole derivatives, and coumarin derivativesare known to show electro-luminescence. Semiconductive conjugatedpolymers have also been used as electroluminescent materials, as hasbeen disclosed in, for example, Friend et al, U.S. Pat. No. 5,247,190,Heeger et al., U.S. Pat. No. 5,408,109, and Nakano et al., PublishedEuropean Patent Application 443 861. The organic materials can betailored to provide emission at various wavelengths. However, theyfrequently are degraded by atmospheric gases, particularly oxygen andwater vapor. This sensitivity can severely limit the working lifetime ofthe device if the materials are not properly sealed.

[0007] Typically, the device is fabricated on a glass substrate and thenhermetically sealed with epoxy to another sheet of glass. In Nakamura etal, U.S. Pat. No. 5,427,858, an electroluminescent device has aprotection layer of a fluorine-containing polymer which is optionallycovered with a glass shield layer. In Tang, U.S. Pat. No. 5,482,896, amaterial such as an epoxy or hot melt adhesive is used to seal the edgesof an electroluminescent device between a rigid support and a thin(25-50 micron) glass substrate. In Scozzafava et al., U.S. Pat. No.5,073,446, an electroluminescent device including a glass substrate hasan outer capping layer comprised of fused metal particles containing atleast 80% indium, in order to prevent oxidation of the second electricalcontact layer. However, having glass as a substrate greatly increasesthe fragility of the device. Moreover, devices having a glass substratesare not flexible at or below room temperature and therefore cannot beconformed to curved surfaces.

[0008] Therefore, there is a need to improve the chemical stability oflayers in organic electronic devices that are sensitive to environmentalelements. There is also a need to improve the durability as well as theflexibility of such devices.

SUMMARY OF THE INVENTION

[0009] The present invention relates to a method for improvingresistance to oxygen and moisture degradation of a flexible organicelectronic device and to a flexible organic electronic device havinggreatly improved resistance to environmental degradation, particularlyoxygen and moisture degradation, and improved durability. The deviceincludes an organic active layer sandwiched between two electricalcontact layers, the sandwich being sealed between two flexible compositebarrier structures. The flexible composite barrier structures haveoxygen and water vapor transport rates of preferably less than 1.0cc/m²/24 hr/atm.

[0010] In one embodiment of the invention, the device comprises in theorder listed:

[0011] (a) a first flexible composite barrier structure comprising atleast one layer of a first polymeric film and at least one layer of afirst barrier material;

[0012] (b) at least one first electrical contact layer;

[0013] (c) at least one active layer comprising an organic activematerial, said active layer having dimensions defined by a length and awidth;

[0014] (d) at least one second electrical contact layer;

[0015] (e) a second flexible composite barrier structure comprising atleast one layer of a second polymeric film and at least one layer of asecond barrier material;

[0016] wherein at least one of the first and second composite barrierstructures is light-transmitting, and further wherein the first andsecond composite barrier structures are sealed together, to envelop theactive layer.

[0017] In a second embodiment, the device includes a portion of thefirst electrical contact layer and a portion of the second electricalcontact layer which extend beyond the dimensions of the active layer,and the first and second composite barrier structures are further sealedto the portion of the first electrical contact layer and the portion ofthe second electrical contact layer that extend beyond the dimensions ofthe active layer.

DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a schematic diagram of a top view of an organicelectronic device of the invention.

[0019]FIG. 2 is a schematic diagram of a cross-section at line 2-2 ofthe device of FIG. 1 before the device is sealed.

[0020]FIG. 3 is a schematic diagram of a top view at line 3-3 of thedevice shown in FIG. 2.

[0021]FIG. 4 is a schematic diagram of a cross-section at line 2-2 ofthe device of FIG. 1 after it is sealed.

[0022]FIG. 5 is a plot of peel strength versus distance when peelingapart a composite barrier structure of the invention sealed to a patternof electrodes on a polymeric support.

[0023]FIG. 6 is a schematic diagram of a composite barrier structurebeing peeled from a support and an electrode material.

[0024]FIG. 7(a) is a plot of light emission of a polymer light emittingdevices of the present invention at initial time and after fifty days ofambient storage.

[0025]FIG. 7(b) is a plot of light emission of a polymer light emittingdevices without out the barrier structure of the present invention, atinitial time and after fifty days of ambient storage.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The present invention relates to a device having at least, in theorder listed, a first flexible composite barrier structure; a firstelectrical contact layer, a layer containing at least one organic activematerial; a second electrical contact layer; and a second flexiblecomposite barrier structure.

[0027] It is understood that it is necessary to be able to connect theelectrical contact layers of the device to external circuitry in orderfor the device to function.

[0028] In most cases this circuitry connection can be accomplished byextending the electrical contact layers beyond the dimensions of theactive layer for the connection. The composite barrier structures arethen sealed together and to the extended portion of the electricalcontact layers, with the electrical contact layers continuing beyond theseal. However, it is also possible to use conductive pathways known asvias to connect the electrical contact layers to external circuitry. Thevia openings can either be formed in each layer as the device isassembled, or formed by drilling through all the layers after the deviceis assembled. The openings are then plated through using well-knowntechniques described in, for example, Sinnadurai, Handbook ofMicroelectronic Packaging and Interconnection Technologies(Electrochemical Publications Ltd., 1985). If vias are used, theopenings should be completely sealed around the connecting wires toprotect the active layer from exposure to the external environment.

[0029] As used herein, the term “flexible” is intended to mean that aplanar sheet of the material is less rigid than glass having a thicknessof 1 millimeter at room temperature and preferably can be bent at anangle of at least 10° from the plane without breaking. The term“light-transmitting” is intended to mean that the material transmits atleast 50% of light in the visible spectrum (400-700 nm). The term“barrier” is intended to mean low permeability to oxygen and watervapor.

[0030] The term “essentially X” is used to mean that the composition ofa particular material is mainly X, and may also contain otheringredients that do not detrimentally affect the functional propertiesof that material to a degree at which the material can no longer performits intended purpose.

[0031] When layer A is stated to be “adjacent to” a first surface oflayer B, it is meant that layer A is closer to a first surface of layerB than it is to a second surface of layer B, such second surface beingdisposed opposite of the first surface. As used herein, the word“adjacent” does not necessarily mean that layer A is immediately next tothe first surface of layer B. Thus, it is entirely possible that a layerC is disposed between layer A and layer B, and it is still true thatlayer A is adjacent to the first surface of layer B.

[0032] FIGS. 1-4 show one example of an organic electronic device 10according to the invention. As best seen in FIGS. 2 and 4, the device 10includes a first flexible composite barrier structure 20, a firstelectrical contact layer 30, an active layer 40, a second electricalcontact layer 50 and a second flexible composite barrier structure 60.Depending upon the intended application, the device 10 can be connecteddirectly to an electrical source 100, 120, as best seen in FIGS. 1 and3. Alternatively, device 10 may be connected to at least one externalcircuit (not shown) and thereby be a part of an overall electronicsystem (not shown).

[0033] As best seen in FIGS. 2 and 4, the first composite barrierstructure 20 has an inner surface 24 and is made up of two polymericlayers 21A and 21B on either side of a layer of barrier material 22. Thepatterned first electrical contact layer 30 is placed adjacent to theinner surface 24 of the first composite barrier structure 20. As bestseen in FIGS. 1 and 3, the first electrical contact layer patternconsists of lines across the width 44 of the active layer and extendingbeyond an edge 43A of the active layer 40. The first electrical contactlayer 30 extends beyond the dimensions of the active layer 40 in areas31. As best seen in FIGS. 2 and 4, the patterned second electricalcontact layer 50 is adjacent to a second surface 48 of the active layer40 opposite the surface 46 adjacent to the first electrical contactlayer 30, such that the active layer 40 is sandwiched between the secondelectrical contact layer 50 and the first electrical contact layer 30.As best seen in FIGS. 1, 2 and 4, the second electrical contact layerpattern consists of lines across to the length 42 of the active layer,and extending beyond another edge 45A, 44 of the active layer 40. Asbest seen in FIGS. 1 and 2, the second electrical contact layer extendsbeyond the dimensions of the active layer in area 52. As best seen inFIGS. 2 and 4 the second flexible composite barrier structure 60 is madeup of two polymeric layers 61A and 61B on either side of a layer ofbarrier material 62. On the inner surface 64 of the second barrierstructure is an adhesive layer 70

[0034] It is understood that the electrical contact layers 30, 50 mayextend beyond any one or more of the active layer edges 43A, 43B, 45A,45B, depending on the design of the device 10.

[0035] It is understood that FIGS. 1-4 have been drawn to represent therelative order of the layers, exaggerating their separation, and are notan accurate depiction of their relative dimensions.

[0036] As best seen in FIGS. 1, 2, and 4, the dimensions 65, 66 of thesecond composite barrier structure 60 can be smaller than the dimensions26, 27 of the first composite barrier structure 20. In the illustratedembodiment the dimensions 65, 66 of the second composite structure 60are greater than the dimensions 42, 44 of the active layer 40 (notshown) in order to effectively seal the active layer 40. In anembodiment (not shown) wherein at least one of the electrical contactlayers is also sensitive to environmental degradation, the dimensions ofthe composite barrier structures should be adjusted to also effectivelyseal the sensitive electrical contact layer(s). It is thus understoodthat the relative dimensions 65, 66 of the second composite barrierstructure 60 and the dimensions 26, 27 of the first composite barrierstructure 20 may vary so long as the composite barrier structures 20, 60can provide an effective seal for the device 10.

[0037] As best seen in FIG. 4, the first and second flexible compositebarrier structures 20 and 60 are sealed together by means of adhesivelayer 70 outside the dimensions of active layer 40, at region 102.Although not explicitly shown in the drawings, the first and secondflexible composite barrier structures 20 and 60 are sealed at all edgessuch that the active layer 40 is completely enveloped within the sealededges. Preferably, the first and second flexible composite barrierstructure 20 and 60 are sealed in a way that also envelopes all portionsof the first and second electrical contact layers 30, 50, except forarea 31 of the first electrical contact layer 30 and area 52 of thesecond electrical contact layer 50.

[0038] In the embodiment wherein device 10 is a light-emitting diode,layer 30 can be a cathode (or an anode), layer 40 is a light-emittinglayer containing an electroluminescent material, and layer 50 is therespective counterpart electrode, i.e.: an anode (or a cathode), as thecase may be.

[0039] 1. Flexible Composite Barrier Structures

[0040] The flexible composite barrier structures 20 and 60 are acomposite of at least one polymeric film layer and at least one layer ofbarrier material. The two composite barrier structures can be made ofthe same or different material. At least one of the two composite layersshould be light-transmitting, preferably transmitting at least 80% inthe visible region.

[0041] The polymeric film 21A, 21B, 61A, 61B useful in the invention isdimensionally and physically stable under the operating conditions ofthe device. Examples of suitable polymers include materials containingessentially polyolefins, such as polyethylene and polypropylene;polyesters such as polyethylene terephthalate and polyethylenenaphthalate; polyimides; polyamides; polyacrylonitrile andpolymethacrylonitrile; perfluorinated and partially fluorinated polymerssuch as polytetrafluoroethylene and copolymers of tetrafluoroethyleneand 2,2-dimethyl-1,3-dioxole; polystyrenes; polycarbonates; polyvinylchloride; polurethanes; polyacrylic resins, including homopolymers andcopolymers of esters of acrylic and/or methacrylic acid; epoxy resins;and novolac resins. More than one layer of polymeric film can be usedand combinations of films with different compositions can be used. Themultiple layers can be joined together with appropriate adhesives or byconventional layer producing processes such as known coating and/orco-extrusion processes. The polymeric films generally have a thicknessin the range of about 0.5-10 mils (12.7-254 microns). When more than onefilm layer is present, the individual thicknesses can be much less.

[0042] It is understood that although the polymeric film 21A, 21B, 61A,61B contains essentially the polymers described above, these films mayalso include conventional additives. For example, many commerciallyavailable polymeric films contain slip agents or matte agents to preventthe layers of film from sticking together when stored as a large roll.In some cases, the size of such additive may cause irregularities anddefects in the adjoining layer of barrier material; such irregularitiesmay detrimentally affect the barrier properties of the composite barrierstructure. Where the additives detrimentally affect the compositebarrier structure, a polymeric film which is free of slip and mattingagents, or in which such agents are small or unobtrusive with respect tothe desired thickness of the layer of barrier material 22, 62 ispreferred. In some cases, slip coatings can be used.

[0043] In the composite structures 20, 60 of the invention, it ispreferred to have at least one layer of barrier material 22, 62sandwiched between at least two layers of polymeric film 21A, 21B, 61A,61B, as best seen in FIG. 4. Such a composite structure 20, 60 allowsfor very thin and flexible layers of barrier material which are thenprotected by the outer layers of polymeric film from damage. There maybe more than one layer of barrier material (not shown), each layer maybe positioned between two polymeric layers. The barrier layer can beapplied to the first layer of polymeric film by one of the processesdescribed below. The second layer of polymeric film can then be appliedby lamination or coating, casting or extrusion processes. The secondpolymeric film layer can be of the same or different composition fromthe first. For example, a polyester film 1-2 mils (25.4-50.8 microns)thick can be coated with a 2-500 nm thick layer of silicon nitride(SiN_(x)) using plasma enhanced chemical vapor deposition. This layercan then be overcoated with a solution of acrylic resin which is allowedto dry, or an epoxy or novolac resin followed by curing. Alternatively,the silicon nitride coated polyester film can be laminated to a secondlayer of polyester film. The overall thickness of the compositestructure is generally in the range of about 0.5-10 mils (12.3-254microns), preferably 1-8 mils (25.4-203.2 microns). Such overallthickness is affected by the method used to apply or lay down thecomposite structure.

[0044] As best seen in FIGS. 2 and 4, an adhesive 70 is generallyapplied to at least one surface of the composite structures 20, 60. Thecomposite barrier structures 20, 60 are sealed with the adhesive bybringing the inner surfaces 24, 64 of the structures 20, 60 together.The adhesive 70 should be capable not only of sealing the two compositestructures together, but of sealing with at least the portion of theelectrical contact layers 31, 52 extending beyond the dimensions of theactive layer 40. It is understood that an adhesive layer (not shown) maybe placed next to the inner surface 24 of the first composite barrierstructure 20 in addition to, or instead of adhesive layer 70.

[0045] In another embodiment, an adhesive component can be incorporatedin at least one of the polymeric films 21A, 61B adjacent to the activelayer 40 instead of or in addition to the separate adhesive layer 70. Insuch a case, a separate adhesive layer 70 may not be necessary to sealthe composite barrier structures 20, 60 together.

[0046] Suitable adhesives, useful as a separate layer (such as layer 70)and/or as a component of one of the polymeric film layers 21A, 61Binclude materials containing essentially polymer adhesive resins,amorphous polyesters, copolyesters, polyester blends, nylon,polyurethanes and polyolefins, including polyethylene, polypropylene,polyethylene vinyl alcohol, ethylene vinylacetate copolymer, copolymersof ionomers and acids. It is understood that, where the adhesive layeris adjacent to a light-transmitting layer, the adhesive layer shouldalso be light-transmitting. Similarly, an adhesive component to beincorporated into a light-transmitting polymeric film layer should notdetrimentally affect the light-transmitting property of the polymericfilm layer.

[0047] The barrier material useful in the barrier layers 22, 62 of theinvention can be a substance that, when formed as a continuous film 1000Å in thickness, has an oxygen and water vapor transport rate of lessthan 1.0 cc/m²/24 hr/atm, preferably less than 0.2 cc/m²/24 hr/atm.Suitable barrier materials include malleable and crack resistantmaterials that are capable of flexing. Examples of such materialsinclude those containing essentially metals, such as aluminum, nickel,copper, tin and stainless steel, as well as alloys. The barrier materialcan also be any inorganic materials that are chemically stable to waterand oxygen, including inorganic oxides, nitrides, fluorides, andcarbides, such as those of silicon, aluminum, indium, titanium,magnesium, hafnium, tantalum, and zirconium, and combinations thereof.

[0048] Each of the barrier layers 22, 62 should be a continuous layerthat contains a minimal number of defects that increase the material'soxygen and water vapor permeability characteristics so that it can nolong function as a barrier. Thus, for example, defects such as pinholesor cracks would be undesirable. It is understood that in addition to thesize of defect, the area density of defect (i.e., number of defects perunit area) also may affect the functional characteristics of the barriermaterial. In order to maintain flexibility, the layer of barriermaterial generally has a thickness no greater than 1 micron, preferablyno greater than 500 nm. In general, the barrier layer may have athickness in the range of 2-500 nm. However, with some flexible metalfilms, such as Al foils it is possible to use barrier layers thickerthan the preferred ranges.

[0049] The barrier layers of the invention are composites containingvery thin layers of materials having very low permeability.

[0050] The specific choice of polymeric film and barrier material willdepend on the processing conditions to which the composite structurewill be exposed and the light-transmission requirements. When thecomposite structure 20 or 60 is used as a support with additional layersbuilt upon it, it may undergo various processing conditions includingvapor deposition processing and/or wet chemical etching. In some casesthe polymeric film will be the outer layer of the composite structurewhich is exposed to further processing. If they are subjected tochemical etching conditions, materials such as polyesters, polyimides,and fluorinated polymers are preferred polymeric materials. When theprocessing involves vapor deposition steps, it is preferred that thepolymeric film be a polyimide with high a glass transition temperature(Tg) (e.g., Tg of from 100° C. to 350° C.) or a polyester, morepreferably, polyethylene naphthalate. In some cases the barrier materialwill be the outer layer of the composite structure that is exposed tofurther processing. The barrier material should be chosen to withstandthese conditions. When the composite structure 20 or 60 is added as alast layer, it often will not undergo any further processing. Therefore,the range of choices for the composition of components in the compositebarrier structure 20 or 60 placed as a last layer is much broader.

[0051] When the composite structure 20 or 60 is adjacent to a lighttransmitting electrical contact layer, the composite barrier structureshould also be light-transmitting in order to transmit light into thedevice or transmit light generated by the device. Any light-transmittinglayer of barrier material can be used in this case, including glassesand inorganic oxides, nitrides, fluorides, and carbides with band gapsgreater than 2.5 eV. Particularly preferred light transmitting barriermaterial are glasses, such as materials essentially made of siliconnitrides having formula (I) below; silicon oxides having formula (II)below; aluminum oxides having formula (III) below; aluminum nitrideshaving formula IV below:

SiN_(w), wherein w is between 0.8 and 1.2, inclusive  Formula (I)

SiO_(x), wherein w is between 1.5 and 2.0, inclusive  Formula (II)

AlO_(y), wherein y is between 1 and 1.5, inclusive  Formula (III)

AlN_(z), wherein z is between 0.8 and 1.2, inclusive  Formula (IV)

[0052] Also combinations of suitable materials can be used.

[0053] When the composite structure is adjacent to an opaque electricalcontact layer, there is no need for a light-transmitting compositebarrier structure.

[0054] To summarize, there are at least the following four types ofcomposite barrier structures that can be used depending on the placementof the structure in the device: (i) the composite barrier structure isused as a support upon which additional layers are processed and isadjacent to a light-transmitting electrical contact layer; (ii) thecomposite barrier structure is used as a support upon which additionallayers are processed and is adjacent to an opaque electrical contactlayer; (iii) the composite barrier structure is the last layer appliedand is adjacent to a light-transmitting electrical contact layer; and(iv) the composite barrier structure is the last layer applied and isadjacent to an opaque electrical contact layer. The choice of materialsused in the component layers of the composite barrier structure is inpart dependent upon the type of composite structure.

[0055] The polymeric film layer 21A, 21B, 61A, 61B and the barriermaterial 22, 62 can be combined together using any known applicationtechnique that will produce the desired thicknesses and uniformity,including coating processes such as spin coating and spray coating,extrusion coating, casting, screen printing, and vapor depositionprocesses. A preferred process is to apply the barrier material 22, 62to the polymeric film 21A or 21B, 61A or 61B, respectively, by a vapordeposition process. Such processes include chemical vapor deposition andplasma enhanced chemical vapor deposition, and physical depositionprocesses such as evaporation, ion-plating and sputtering. Plasmaenhanced chemical vapor deposition is particularly preferred as itcauses less heating of the substrate (in this case, the polymeric film21A, 21B, 61A, or 61B), and the coating flux is more uniform. It therebyprovides essentially defect-free layers.

[0056] 2. First Electrical Contact Layer

[0057] The first electrical contact layer 30, is applied to one surfaceof the first flexible composite barrier structure. This electricalcontact layer can include any material capable of injecting (orcollecting) charge carriers into (or from, as the case may be) theactive layer 40.

[0058] Although not shown in the drawings, the first electrical contactlayer can be made of one single layer of material or can be a compositeof multiple layers of first electrical contact layer material. Where thefirst electrical contact layer is an anode, (i.e., an electrode that isparticularly efficient for injecting or collecting positive chargecarriers) it can be, for example materials containing a metal, mixedmetal, alloy, metal oxide or mixed-metal oxide, or it can be aconducting polymer. Suitable metals include the Group IB metals, themetals in Groups IV, V, and VI, and the Group VIII transition metals. Ifthe first electrical contact layer is to be light-transmitting,mixed-metal oxides of Groups II, III and IV metals, such asindium-tin-oxide, or a conducting polymer, such as polyaniline, can beused.

[0059] Although first electrical contact layer 30 is shown with extendedportions 31 to connect the device to external circuitry, it isunderstood that devices (not shown) that incorporate other means ofcircuitry connection (such as vias) would not require such extendedportions 31. It is further understood that the composition of the firstelectrical contact layer 30 may vary across the dimensions 26, 65 of thecomposite barrier layers 20, 60. For example, where the first electricalcontact layer 30 includes the extended portions 31, parts of theextended portions that are disposed outside of the sealed compositebarrier layers 20, 60 may be contain essentially a material (such asaluminum) that is more resistant to environmental degradation or is abetter conductor than the first electrical contact layer compositionthat is coextensive with the active layer 40. Thus, the first electricalcontact layer composition that is coextensive with the active layer 40may be chosen to provide better electron band-gap matching. At the sametime the first electrical contact layer composition in the extendedportion 31 may be chosen to provide greater conductivity and increasedresistance to environmental degradation outside of the sealed device.The varied composition can be provided by using separate layers of firstelectrical contact layer material, or by adjusting the alloyedcomposition within a first electrical contact layer.

[0060] The first electrical contact layer 30 is usually applied by aphysical vapor deposition process. The term “physical vapor deposition”refers to various deposition approaches carried out in vacuo. Thus, forexample, physical vapor deposition includes all forms of sputtering,including ion beam sputtering, as well as all forms of vapor depositionsuch as e-beam evaporation. A specific form of physical vapor depositionuseful in the present in envention is a rf magentron sputtering.

[0061] In general, the first electrical contact layer will be patterned.It is understood that the pattern may vary as desired. The firstelectrical contact layer can be applied in a pattern by, for example,positioning a patterned mask or photoresist on the first flexiblecomposite barrier structure prior to applying the first electricalcontact layer material. Alternatively, the first electrical contactlayer can be applied as an overall layer and subsequently patternedusing, for example, a photoresist and wet chemical etching. The firstelectrical contact layer typically has a thickness in the range of50-500 nm. First electrical contact layer materials and processes forpatterning that are well known in the art can be used.

[0062] 3. Organic Active Layer

[0063] Depending upon the application of the device 10, the active layer40 can be a light-emitting layer that is activated by an applied voltage(such as in a light-emitting diode), a layer of material that respondsto radiant energy and generates a signal with or without an applied biasvoltage (such as in a photodetector). Examples of photodetectors includephotoconductive cells, photoresistors, photoswitches, phototransistors,and phototubes, and photovoltaic cells, as these terms are describe inMarkus, John, Electronics and Nucleonics Dictionary, 470 and 476(McGraw-Hill, Inc. 1966).

[0064] Where the active layer is light-emitting, the layer will emitlight when sufficient bias voltage is applied to the electrical contactlayers. The light-emitting active layer may contain any organicelectroluminescent or other organic light-emitting materials. Suchmaterials can be small molecule materials such as those described in,for example, Tang, U.S. Pat. No. 4,356,429, Van Slyke et al., U.S. Pat.No. 4,539,507, the relevant portions of which are incorporated herein byreference. Alternatively, such materials can be polymeric materials suchas those described in Friend et al. (U.S. Pat. No. 5,247,190), Heeger etal. (U.S. Pat. No. 5,408,109), Nakano et al. (U.S. Pat. No. 5,317,169),the relevant portions of which are incorporated herein by reference.Preferred electroluminescent materials are semiconductive conjugatedpolymers. An example of such a polymer is poly(p-phenylenevinylene)referred to as PPV. The light-emitting materials may be dispersed in amatrix of another material, with and without additives, but preferablyform a layer alone. The active organic layer generally has a thicknessin the range of 50-500 nm.

[0065] Where the active layer 40 is incorporated in a photodetector, thelayer responds to radiant energy and produces a signal either with orwithout a biased voltage. Materials that respond to radiant energy andis capable of generating a signal with a biased voltage (such as in thecase of a photoconductive cells, photoresistors, photoswitches,phototransistors, phototubes) include, for example, many conjugatedpolymers and electroluminescent materials. Materials that respond toradiant energy and is capable of generating a signal without a biasedvoltage (such as in the case of a photoconductive cell or a photovoltaiccell) include materials that chemically react to light and therebygenerate a signal. Such light-sensitive chemically reactive materialsinclude for example, many conjugated polymers and electro- andphoto-luminescent materials. Specific examples include, but are notlimited to, MEH-PPV (“Optocoupler made from semiconducting polymers”, G.Yu, K. Pakbaz, and A. J. Heeger, Journal of Electronic Materials, Vol.23, pp 925-928 (1994); and MEH-PPV Composites with CN-PPV (“EfficientPhotodiodes from Interpenetrating Polymer Networks”, J. J. M. Halls etal. (Cambridge group) Nature Vol. 376, pp. 498-500, 1995).

[0066] A layer 40 containing the active organic material can be appliedto the first electrical contact layer 30 from solutions by anyconventional means, including spin-coating, casting, and printing. Theactive organic materials can be applied directly by vapor depositionprocesses, depending upon the nature of the materials. It is alsopossible to apply an active polymer precursor and then convert to thepolymer, typically by heating.

[0067] The active layer 40 is applied over the first electrical contactlayer 30, but does not typically cover the entire layer. As best seen inFIG. 2, there is a portion 31 of the first electrical contact layer thatextends beyond the dimensions of the active layer in order to permit theconnection with drive and/or detection circuitry in the finished device.

[0068] 4. Second Electrical Contact Layer

[0069] The second electrical contact layer 50 is applied to the otherside of the active layer 40. Although not shown in the drawings, thesecond electrical contact layer can be made of one single layer ofmaterial or can be a composite of multiple layers of material.

[0070] The second electrical contact layer can be a material containingessentially any metal or nonmetal capable of injecting (or collecting)charge carriers into (or from, as the case may be) the active layer 40.Generally, where the second electrical contact is a cathode (i.e., anelectrode that is particularly efficient for injecting or collectingelectrons or negative charge carriers) the cathode can be any metal ornonmetal having a lower work function than the first electrical contactlayer (in this case, an anode). Materials for the second electricalcontact layer can be selected from alkalil metals of Group I (e.g., Li,Cs), the Group IIA (alkaline earth) metals, the Group II metals,including the rare earths and lanthanide, and the actinides. Materialssuch as aluminum, indium, calcium, barium, and magnesium, as well ascombinations, can be used.

[0071] Although second electrical contact layer 50 is shown withextended portions 52 to connect the device to external circuitry, it isunderstood that devices (not shown) that incorporate other means ofcircuitry connection (such as vias) would not require such extendedportions 52. It is further understood that the composition of the secondelectrical contact layer 50 may vary across the dimensions 27, 66 of thecomposite barrier layers 20, 60. For example, where the secondelectrical contact layer 50 includes the extended portions 52, parts ofthe extended portions that are disposed outside of the sealed compositebarrier layers 20, 60 may be contain essentially a material (such asAluminum) that is more resistant to environmental degradation and/or isa better conductor than the second electrical contact layer compositionthat is coextensive with the active layer 40. Thus, the secondelectrical contact layer composition that is coextensive with the activelayer 40 may be chosen to provide better electron band-gap matching. Atthe same time the second electrical contact layer composition in theextended portion 52 may be chosen to provide greater conductivity andincreased resistance to environment degradation outside of the sealeddevice. The varied composition can be provided by a separate layer ofsecond electrical contact layer material, or could be alloyed within onesecond electrical contact layer.

[0072] The second electrical contact layer is usually applied by aphysical vapor deposition process. In general, the second electricalcontact layer will be patterned, as discussed above in reference to thefirst electrical contact layer 30. Similar processing techniques can beused to pattern the second electrical contact layer. The secondelectrical contact layer typically has a thickness in the range of50-500 nm. Second electrical contact layer materials and processes forpatterning well known in the art can be used.

[0073] A portion 52 of the second electrical contact layer will extendbeyond the dimensions of the light-emitting layer 40. As with the firstelectrical contact layer 30, this extended portion 52 allows for theconnection to drive and/or detection circuitry in the finished device.

[0074] 5. Other Optional Layers

[0075] It is known to have other layers in organic electronic devices.For example, there can be a layer (not shown) between the firstelectrical contact layer 30 and the active layer 40 to facilitateelectrical charge transport and/or electron band-gap matching of thelayers 30, 40 or reduce chemical reactivity between the active layer 40and the first electrical contact layer 30. Similarly, a layer (notshown) can be placed between the active layer 40 and the secondelectrical contact layer 50 to facilitate electrical charge transportand/or electron band-gap matching between the layers 40, 50 or reducechemical reactivity between the active layer 40 and the secondelectrical contact layer 50. Layers that are known in the art can beused. In addition, any of the above-described layers can be made ofmultiple layers. Alternatively, some of all of first electrical contactlayer 30, active layer 40, and second electrical contact layer 50, maybe surface treated to increase charge carrier transport efficiency.Furthermore, additional barrier layers (not shown) can also be placedbetween one of more sets of the layers 20, 30, 40, 50, 60 to protectthem from adverse processing conditions.

[0076] The choice of materials for each of the component layers 21A, 22,22B, 30, 40, 50, 61A, 62, 61B is preferably determined by balancing thegoals of providing a device with high electrooptical efficiency.

[0077] In many instances, organic electronic devices of the inventioncan be fabricated by first applying a first electrical contact layer andbuilding up the device from there. It is understood that it is alsopossible to build up the layers from the second electrical contactlayer.

[0078] The following examples illustrate certain features and advantagesof the present invention.

EXAMPLES

[0079] The following examples are illustrative of the invention, but notlimiting.

Example 1

[0080] A flexible composite barrier structure was formed with polyesterfilm and a thin film barrier of SiN_(x). The SiN_(x) was coated using amicrowave electron cyclotron resonance (ECR) plasma onto a 0.002 inch(50.8 micron) thick film of polyethylene-terephthalate (PET), Mylar®200D supplied by E. I. du Pont de Nemours and Company, Inc. (Wilmington,Del.). Prior to deposition, the chamber was evacuated to a pressure of1.5×10⁻⁷ Torr with a turbo-molecular pump. During deposition, 2 standardcubic centimeters (sccm) of SiH₄, 98 sccm of Ar, and 20 sccm of N₂ wereadmitted into the chamber. The plasma was sustained using 150W ofmicrowave power at 2.455 GHz, while the magnetic field was adjusted toabout 900 Gauss, corresponding to the resonance condition for electronmotion in the plasma. A one hour deposition produced a SiN_(x) filmabout 840 Å thick, as determined by atomic force microscopy (AFM).Chemical depth profiling by X-ray photoelectron spectroscopy (XPS)revealed that films were essentially SiN_(x) (x˜1.15) with some oxygen(˜10%) and presumably some hydrogen (not measurable with XPS)incorporation. The oxygen transport rate (OTR) at 50% relative humiditythrough the coated PET film was evaluated with a commercial instrument(MOCON Oxtran 2/20 made by Mocon, Minneapolis, Minn.) and determined tobe 0.012 cc (O₂)/m²/day/atm. For reference an uncoated film of Mylar®200D has an OTR of about 24 cc (O₂)/m²/day/atm. Therefore the SiN_(x)coating provides a barrier improvement factor of 2000×.

Example 2

[0081] A second flexible composite barrier structure was formed with a200 Å thick film barrier of SiN_(x). The SiN_(x) was coated using amicrowave ECR plasma onto 0.002 inch (50.8 micron) thick Mylar® 200D PETfilm. The gas flow conditions during deposition were 2 sccm of SiH₄, 98sccm of Ar, and 20 sccm of N₂ at a microwave power of 100 W. Thedeposition lasted 30 minutes. The OTR of the SiN_(x) coated PET wassubsequently determined to be 0.12 cc (O₂)/m²/day/atm.

Example 3

[0082] This example illustrates the OTR of a flexible composite barrierstructure having a laminate structure. Lamination of SiN_(x) coated PETprotects the SiN_(x) coating from mechanical damage, which willcompromise barrier properties. PET, 0.002 inch (50.8 micron) thick withabout 1000 A coating of SiN_(x), produced by microwave plasma ChemicalVapor Deposition (CVD), was laminated to uncoated PET, also 0.002 inch(50.8 micron) thick using a commercial adhesive, 3M 8142, from 3M (St.Paul, Minn.). The laminator had a single rubber roll and was operated at48° C. and 35 psi. The final structure of the laminated film wasPET/1000 Å/SiN_(x)/adhesive/PET. The OTR of this laminated structure wassubsequently determined to be 0.00825 cc (O₂)/m²/day/atm.

Example 4

[0083] This example illustrates a flexible composite barrier structurehaving two laminated SiN_(x) layers. Two PET films, each coated withabout 1000 Å of SiN_(x) by microwave plasma enhanced CVD, were laminatedtogether with an adhesive, using the conditions of Example 3, so thatthe SiN_(x) films were to the inside of the structure, and OTR wasmeasured. That is, the structure was PET/SiN_(x)/adhesive/SiN_(x)/PET.Prior to lamination, it was determined that the individual SiN_(x)coated PET films had an OTR of about 0.0075 cc (O₂)/m²/day/atm. The OTRof the laminate structure was less than 0.005 cc (O₂)/m²/day/atm, thelower measuring limit of the MOCON instrument.

Example 5

[0084] This example illustrates the formation of a non-transparentcomposite barrier structure using (a combination of vapor depositedaluminum and layers of barrier polymers is utilized to provide oxygenand moisture barrier) aluminum as the barrier material.

[0085] A first metallized film was prepared with polyvinylidene chloridecopolymer-polyester-aluminum-polyvinylidene chloride copolymer. A rollof Mylar® LB biaxially oriented polyester film was placed in a vacuumchamber where it was unwound and exposed to evaporated aluminum whichcondensed on the film surface to a thickness of 400 Å (or an opticaldensity (OD) of 2.8). The metallized film was then solvent coated with acomposition that was essentially a copolymer of vinylidenechloride/vinyl chloride/methylmethacrylate/acrylonitrile, over the bothsides of the film. The dry coating weight was 1.6 g/m² on both of thecoated sides.

[0086] A second metallized film was prepared by coating Mylar® LB filmwith a polyethyleneimine primer from a 1% solution in water. The driedcoating weight was 0.02 to 0.2 g/m². The primed polyester film was thentopcoated with polyvinyl alcohol in a second coater station. Drypolyvinyl alcohol was diluted to a 10% solutions using 95-98° C. waterand steam sparging to make a coating bath. After cooling, the coatingwas applied using a reverse gravure coating technique. The dry coatingweight was 0.4-1.0 g/m². The product was then aluminum vacuum metallizedas described above on the polyvinyl alcohol side to a thickness of 400 Å(or an OD of 2.8).

[0087] A third “plain” or nonmetallized polyester film was coated on oneside with a 17% solids tetrahydrofuran solution of a mixture ofessentially poly(terephthalic/azeleic acid/ethylene glycol), copolymer.This was the heat sealable layer. The coating was applied by reversemetering coating to a dry coating weight of 6 g/m².

[0088] The first and second metallized films were laminated together viaa solvent based polyurethane adhesive such that the polyvinylidenechloride layer (which was over the aluminum) of the first film wasadjacent to the aluminum layer of the second film. The third polyesterfilm was then laminated to the combination of the first two films via asolvent based polyurethane adhesive such that the plain polyestersurface of the combined first two films was adjacent to the plainpolyester film surface of the third film. The basic overall laminatestructure was omitting the adhesive and primer layers: polyvinylidinechloride copolymer-polyester-aluminum-polyvinylidene chloridecopolymer-aluminum-polyvinyl alcohol-polyester-polyester-solvent coatedpolyester heat sealable layer The OTR was measured to be 0.00062cc/m²/24 hr/atm by an external laboratory.

Example 6

[0089] This example illustrates the bond strength of the heat-sealedcomposite barrier structure.

[0090] The composite barrier structure of Example 5 was heat sealed tothe following second materials representing a second barrier structure:Ex. 6-A: 0.004 inch (50.8 micron) thick PET (400D) Ex. 6-B: 0.004 inch(50.8 micron) thick PET (400D) coated with an unpatterned, electricallyconducting ITO film 1500-2000 Å in thickness Ex. 6-C 0.004 inch (50.8micron) thick PET (400D) coated with patterned ITO lines, 1500-2000 Å inthickness (1 mm line width/0.75 mm spaces).

[0091] The composite barrier structure and the second material werepositioned such that the heat sealable layer was adjacent to the secondmaterial, and adjacent to the ITO layer of the second material, whenpresent. Two 4×4 inch (10.2×10.2 cm) pieces were cut and laid together.These were heat sealed using a Sentinel Brand Machine, Model #12A8-0(manufactured by Packaging Group Inc., Hyannis, Mass.) with adjustabletemperature and timer controls. A one-inch (2.54 cm) seal was attainedat the temperature and dwell times indicated below, applying a pressureof 30 psi.

[0092] To determine bond strength after the heat seal was completed, thesealed structures were cut into strips one inch (2.54 cm) wide.Depending on film thickness, Scotch Red Colored Cellophane Tape (Type650) was applied to the thinner of the sealed substrates to preventbreakage at the seal line. The peel strength was then determined on anInstron Universal Testing Instrument, Model 1122 (available from InstronCorp.). A 5 pound full scale load limit was used with the crossheadspeed set to run at 2 inches (5.1 cm) per minute. The peel strengthswere reported as the average of 4 samples.

[0093] The adhesion tests to patterned ITO were measured bothperpendicular (⊥) and parallel (//) to the ITO lines. Bond strengthswere measured after sealing at either 120° C. or 140° C. for 0.5 or 1.0second. The results are summarized in Table 1 below. TABLE 1 120° C.140° C. Example 0.5 s 1.0 s 0.5 s 1.0 s 6-A  667 g/in. 766 g/in. 864g/in. 881 g/in. 6-B 1276 g/in. 913 g/in. 515 g/in. 358 g/in. 6-C (P-⊥) 554 g/in. 668 g/in. 624 g/in. — 6-C (P-//)  659 g/in. 923 g/in. 916g/in. 988 g/in.

[0094] These peel tests indicate that the polyester heat sealable layerbonds equally well, and under some conditions more strongly, totransparent, conducting ITO compared to bonding to PET alone.

[0095] The adhesion of the composite barrier structure to both electrodematerial and to the support is illustrated in FIGS. 5 and 6. As shown inFIG. 5, the peel strength is plotted versus distance as Sample 6-C (P-⊥)is peeled apart. The peel strength varies with regular peaks and valleyscorresponding to the different materials (electrode material orpolymeric support) that the barrier structure is peeled from. As shownin FIG. 6, the composite barrier structure 300 is peeled alternatelyfrom electrode material 200 and polymeric support 400. If the barrierstructure 300 bonded to only the support material 400 it would beexpected that the plot of peel strength would have a single continuousvalue, without peaks and valleys.

Example 7

[0096] This example illustrates polymer light emitting diode (PLED)device lifetime with a composite barrier structure having siliconnitride barrier layers (Sample 7) as it compares with that of a devicewithout the silicon nitride barrier layer (Comparative sample Y). TenSample 7 devices and ten Comparative Y devices were prepared and tested.

[0097] The basic PLED device structure of both Sample 7 and ComparativeSample Y included a glass substrate with a transparent conducting anodelayer of indium tin oxide over-coated with about 100 nm each of apolymer hole-injecting layer and a yellow light-emitting polymer layer.This was then coated with a thin layer (˜20 nm) of a low work functionmetal and covered with a one micron thick layer of aluminum.

[0098] Sample 7 devices were further fabricated as follows: A singlelayer of 2 mil thick PET (polyethylene terephthalate) about six inchessquare was coated consecutively on both sides with a silicon nitridebarrier layer about 80 nm thick. The silicon nitride layers weredeposited by microwave, plasma-enhanced (electron cyclotron resonance(ECR)) chemical vapor deposition (CVD). The conditions during depositionwere 150 watts microwave power, 2.7 sccm of silane (SiH4), about 100sccm of Ar, and 20 sccm of N2. The silicon nitride coated PET was thenlaminated to another 2 mil thick sheet of non-coated PET using a 2 milthick, commercial adhesive, as described in Example 3 above, to form thecomposite barrier structure. Sections of the laminate composite barrierstructure, 35 mm×25 mm, were then cut and used to seal PLED devices ofabout the same area, using a commercial, ultraviolet curable epoxy. Agood barrier can prevent device degradation caused by atmospheric gasesinfiltrating the device.

[0099] Comparative Sample Y devices were further prepared as follows:similar PLED devices were also epoxy sealed with a similar PET laminate,but without barrier layers of silicon nitride.

[0100] The light emission of Sample 7 and Comparative Sample Y deviceswas measured four (4) days after device fabrication (storage at ambientconditions) and then measured again after storing the devices in ambientconditions for fifty (50) days after device fabrication.

[0101]FIG. 7(a) shows a plot of light emission of Sample 7 photodiodesinitially (500) and then Sample 7 light emission after fifty (50) days(502). There was essentially no change in the light emission of thesedevices.

[0102] In contrast, the performance of Comparative Sample Y devices ismarkedly different. FIG. 7(b) shows a plot of light emission ofComparative Sample Y photodiodes initially (600) and then Sample Y lightemission after 50 days (602). The light emission was significantlyreduced after fifty (50) days of ambient storage.

What is claimed is:
 1. A flexible organic electronic device comprisingin the order listed: a) a first flexible composite barrier structurecomprising at least one layer of a first polymeric film and at least onelayer of a first barrier material, the first barrier structure having afirst inner surface; b) at least one first electrical contact layer; c)at least one active layer comprising an organic active material, saidactive layer having dimensions defined by a length and a width; d) atleast one second electrical contact layer; e) a second flexiblecomposite barrier structure comprising at least one layer of a secondpolymeric film and at least one layer of a second barrier material, thesecond barrier structure having a second inner surface; wherein at leastone of the first and second composite barrier structures islight-transmitting; wherein the first and second composite barrierstructures are sealed together to envelop the at least one active layer.2. The device of claim 1 wherein a portion of the first electricalcontact layer and a portion of the second electrical contact layerextend beyond the dimensions of the active layer, wherein the first andsecond composite barrier structures are also sealed to the extendedportions of the first and second electrical contact layers.
 3. Thedevice of claim 1 wherein the one second electrical contact layercomprises a material having a lower work function than the firstelectrical contact layer.
 4. The device of claim 1 wherein the firstelectrical contact layer is an anode and the second electrical contactlayer is a cathode.
 5. The device of claim 1 wherein the first andsecond polymeric films of the first and second composite barrierstructures are selected from polyolefins, polyesters, polyimides,polyamides, polyacrylonitrile and polymethacrylonitrile; perfluorinatedand partially fluorinated polymers, polycarbonates, polyvinyl chloride,polurethanes, polyacrylic resins, epoxy resins, and novolac resins. 6.The device of claim 1 wherein the first and second barrier materials areindependently selected from metals, metal alloys, inorganic oxides,inorganic nitrides, inorganic carbides, inorganic fluorides, andcombinations thereof.
 7. The device of claim 1 wherein the firstflexible composite barrier structure and the first electrical contactlayer are light-transmitting.
 8. The device of claim 7 wherein the firstand second polymeric films in the first composite barrier material areselected from polyethylene terephthalate, polyethylene naphthalate,polyimide, and combinations thereof.
 9. The device of claim 1 whereinthe barrier material is selected from aluminum, nickel, chromium,copper, tin, stainless steel, and alloys thereof.
 10. The device ofclaim 1 wherein the a barrier material selected from inorganic oxides,inorganic nitrides, inorganic fluorides, inorganic carbides, andcombinations thereof.
 11. The device of claim 1 wherein the layer offirst and second barrier materials has a thickness in the range of 2-500nm.
 12. The device of claim 1 wherein the first flexible compositebarrier structure comprises two layers of polymeric film with a layer ofthe first barrier material therebetween.
 13. The device of claim 1wherein the second flexible composite barrier structure comprises twolayers of polymeric film with a layer of the second barrier materialthere between.
 14. The device of claim 1 wherein the first flexiblecomposite barrier structure further comprises a layer of adhesive on thefirst inner surface.
 15. The device of claim 1 wherein the secondflexible composite barrier structure further comprises a layer ofadhesive on the second inner surface.
 16. The device of claim 1 whereinat least one of the first inner surface and the second inner surfacecontains an adhesive component.
 17. The device of claim 14 or claim 15wherein the adhesive is selected from polymer adhesive resins, amorphouspolyesters, copolyesters, polyester blends, nylon, polyurethanes,polyolefins, vinyl alcohol, ethylene vinylacetate copolymer, copolymersof ionomers and acids, and combinations thereof.
 18. The device of claim16 wherein the adhesive component is selected from polymer adhesiveresins, amorphous polyesters, copolyesters, polyester blends, nylon,polyurethanes, polyolefins, vinyl alcohol, ethylene vinylacetatecopolymer, copolymers of ionomers and acids, and combinations thereof.19. The device of claim 1, wherein the active layer includeselectroluminescent material.
 20. The device of claim 1, wherein theactive layer includes a conjugated polymer.
 21. An electroluminescentdisplay containing the device of claim
 1. 22. A photodetector containingthe device of claim
 1. 23. A method for improving resistance to oxygenand moisture degradation of a flexible organic electronic devicecomprising at least one first electrical contact layer having a firstelectrical contact layer outer surface and an opposite first electricalcontact layer inner surface, at least one active layer adjacent to thefirst electrical contact layer inner surface, the active layercomprising an organic active material, said active layer having a set ofdimensions, and at least one second electrical contact layer having asecond electrical contact layer outer surface and an opposite secondelectrical contact layer inner surface, wherein the second electricalcontact layer inner surface is adjacent to the active layer, the methodcomprising the steps of: placing a first flexible composite barrierstructure adjacent to the at least one first electrical contact layerouter surface, the first flexible composite barrier structure comprisingat least one layer of a first polymeric film and at least one layer of afirst barrier material, the first barrier structure having a first innersurface; placing a second flexible composite barrier structure adjacentto the at least one second electrical contact layer outer surface, thesecond flexible composite barrier structure comprising at least onelayer of a second polymeric film and at least one layer of a secondbarrier material, the second barrier structure having a second innersurface; wherein at least one of the first and second composite barrierstructures is light-transmitting, sealing the first inner surface andthe second inner surface together outside the dimensions of the activelayer to envelop the active layer.
 24. The method of claim 23 wherein aportion of the first electrical contact layer and a portion of thesecond electrical contact layer extend beyond the dimensions of theactive layer, wherein the first and second composite barrier structuresare also sealed to the extended portions of the first and secondelectrical contact layers.
 25. The method of claim 23 wherein the secondelectrical contact layer comprises a material having a lower workfunction than the first electrical contact layer.
 26. The method ofclaim 23 wherein the first electrical contact layer is a cathode and thesecond electrical contact layer is an anode.
 27. The method of claim 23wherein the first and second polymeric films of the first and secondcomposite barrier structures are selected from polyolefins, polyesters,polyimides, polyamides, polyacrylonitrile and polymethacrylonitrile;perfluorinated and partially fluorinated polymers, polycarbonates,polyvinyl chloride, polurethanes, polyacrylic resins, epoxy resins, andnovolac resins.
 28. The method of claim 23 wherein the first and secondbarrier materials are selected from metals, metal alloys, inorganicoxides, inorganic nitrides, inorganic carbides, inorganic fluorides, andcombinations thereof.
 29. The method of claim 23 wherein the firstflexible composite barrier structure and the first electrical contactlayer are light-transmitting.
 30. The method of claim 23 wherein thefirst and second polymeric films in the first composite barrier materialis selected from polyethylene terephthalate, polyethylene naphthalate,polyimide, and combinations thereof.
 31. The method of claim 23 whereinthe barrier material is selected from aluminum, nickel, chromium,copper, tin, stainless steel, and alloys thereof.
 32. The method ofclaim 23 wherein the barrier material selected from inorganic oxides,inorganic nitrides, inorganic fluorides, inorganic carbides, andcombinations thereof.
 33. The method of claim 23 wherein the layer offirst and second barrier materials has a thickness in the range of 2-500nm.
 34. The method of claim 23 wherein the first flexible compositebarrier structure comprises two layers of polymeric film with a layer ofthe first barrier material therebetween.
 35. The method of claim 23wherein the second flexible composite barrier structure comprises twolayer of polymeric film with a layer of the first barrier materialtherebetween.
 36. The method of claim 23 wherein the first flexiblecomposite barrier structure further comprises a layer of adhesive on thefirst inner surface.
 37. The method of claim 23 wherein the secondflexible composite barrier structure further comprises a layer ofadhesive on the second inner surface.
 38. The method of claim 23 whereinat least one of the first inner surface and the second inner surfacecontains an adhesive component.
 39. The method of claim 36 or 37 whereinthe adhesive is selected from polymer adhesive resins, amorphouspolyesters, copolyesters, polyester blends, nylon, polyurethanes,polyolefins, vinyl alcohol, ethylene vinylacetate copolymer, copolymersof ionomers and acids, and combinations thereof.
 40. The method of claim38 wherein the adhesive component is selected from polymer adhesiveresins, amorphous polyesters, copolyesters, polyester blends, nylon,polyurethanes, polyolefins, vinyl alcohol, ethylene vinylacetatecopolymer, copolymers of ionomers and acids, and combinations thereof.41. The method of claim 23, wherein the active layer includeselectroluminescent material.
 42. The method of claim 23, wherein theactive layer includes a conjugated polymer.